This invention relates to a public address system, a control unit of a public address system and a monitoring device of a public address system.
Public address systems are sound systems informing and entertaining the public in buildings or public places, e.g. airports. In an event of emergency public address systems also warn the public. Public address systems consist of lines of loudspeakers and amplifiers. Monitoring the connection and correctness of one loudspeaker line from the amplifier to one end point of the loudspeaker line is required to meet the standard EN 60849 for voice evacuation systems. In current public address systems this is achieved for example by monitoring endpoints of loudspeaker lines by DC current through the wire or the shielding of the wire by sending continuously a unique signal back from one endpoint of the speaker line to the amplifier. Other examples are impedance measurement or monitoring with use of extra wiring.